Revert "handled case of assets union (#3060)"

This reverts commit 2bff5d1.

Author: nitzanyiz

src/assets/Assets.ts

@@ -1,5 +1,5 @@
 import _ from 'lodash';
-import type {AssetRecord} from '../typings/assets';
+import {PathRecord} from '..//typings/common';
 
 interface CustomObject {
   [key: string]: any;
@@ -42,7 +42,7 @@ function ensurePath(obj: CustomObject, path: string) {
 export class Assets {
   [key: string]: any;
 
-  loadAssetsGroup<T extends string, K extends object>(groupName: T, assets: K): asserts this is AssetRecord<typeof this, T, K> {
+  loadAssetsGroup<T extends string, K extends object>(groupName: T, assets: K): asserts this is PathRecord<T, K> {
     if (!_.isString(groupName)) {
       throw new Error('group name should be a string');
     }

src/typings/assets.d.ts

@@ -10,3 +10,14 @@ export type ExtendTypeWith<T extends Constructor<any>, OtherObject extends objec
 export type Dictionary<TYPE> = {[key: string]: TYPE};
 
 export type ComponentStatics<T> = Pick<T, keyof T>;
+
+type DotExtendedString<T extends string> = `${T}.`;
+export type PathArray<S extends string> = DotExtendedString<S> extends `${infer A}.${infer B}` ?
+  A extends '' ? [] : [A, ...PathArray<B>]
+  : [];
+
+export type RecRecord<Path extends string[], K = {}> = Path extends [infer Next, ...infer Rest] ?
+  {[P in Next] : RecRecord<Rest, K>}
+  : K;
+
+export type PathRecord<T extends string, K = {}> = RecRecord<PathArray<T>, K>;